In a common structure 100 such as a building, a vertical reactive force acting on column bases 101 against a permanent load (a dead load permanently acting thereon, including the weight of the structure and a superimposed load) is substantially evenly balanced in a planar direction, and a vertical force R substantially evenly acts on seismic isolators when the structure is seismically isolated (see FIG. 12A). However, when a horizontal force is exerted by an earthquake and thus an overturning moment is exerted, a pullout (tensile) force tends to prevail at an end E of the structure 100. Therefore, the seismic isolators at the end E of the common structure 100 are provided with a pullout countermeasure (see FIGS. 12B and 12C).
In the case of a plant support structure such as a boiler steel frame, however, a vertical reactive force on the column bases is unevenly balanced in a planar direction due to the load of equipment to be supported, so that a pullout force does not always act on the end of the structure. Thus, in the case of a plant support structure, the position where a pullout countermeasure should be provided cannot be uniformly determined to be the end as in a common structure.
For example, Japanese Patent Laid-Open No. 10-325261 and Japanese Patent Laid-Open No. 2005-61565 disclose proposals pertaining to a pullout countermeasure.
Japanese Patent Laid-Open No. 10-325261 proposes providing a high-rise building with an internal space that penetrates stories at a center part and supporting the building with laminated rubber bearings having an allowable value of long-term contact pressure of 150 to 300 kg/cm2. According to this proposal, the building is provided with the internal space so that, compared with a building that has the same area of occupation and does not have an internal space, a long-term load on a lower part of the building is largely imposed on the laminated rubber bearings at peripheral edges. This makes it less likely that the building is overturned or that a pullout force occurs on the laminated rubber bearings.
Japanese Patent Laid-Open No. 2005-61565 proposes a laminated rubber bearing having a laminated rubber and flanges on the upper and lower sides thereof, in which the bending rigidity of the upper and lower flanges is set to such rigidity that the flanges can undergo out-of-plane bending deformation under an axial tensile force smaller than an axial tensile force that is large enough to damage the laminated rubber. According to this proposal, when a lift occurs in a superstructure, before a damaging vertical pullout force acts on the laminated rubber, the upper and lower flanges, which have lower rigidity than the laminated rubber, undergo bending deformation while exerting a resisting force according to a vertical shift, so that the risk of the pullout force acting on the laminated rubber can be eliminated or reduced.